AS most of the users. Picajet is not my only tool used for searching/browsing/editing my pictures. As such, i think picajet should detect file changes and reimport IPTC/XMP info from those files.
Have a look at following scenario.
Open picasa and picajet simutaniously. And make the watch the same test folder containing 10 pictures.

Attach a category to the pictures using picajet and save it in the metada by pressing Ctrl-Shift-I.
Watch how picasa discovers the change and notifies the user by showing the "updating thumbnail" window.
In Picasa Press Ctrl-K (keyword) on the image to see that it has indeed detected the new metadata which enables you to search for it in the search panel.
Open an image file in Windows Explorer Check date/time
Add an extra keyword within picasa.
check that date/time has changed.
Go back to picajet.. ..
Wait...
Noting happens ..
Open the Metadata window on the image [shift-enter].
Check the keywords property in IPTC section. to detect that indeed picasa has made changes to the keyword.
(Do no click on the keyword list, there is a bug here that will degrade all your keyword to only the first keyword in the list.)
Check the Categories in the "properties" panel..
The keword changes where not converted into categories.
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